Perovskite lithium and bismuth modified potassium-sodium niobium lead-free ceramics for high temperature applications

[(K (1-x) 2 Na (1-x) 2 Lix) 1-3y Biy] Nb O3 (abbreviated as KNLBN) ceramics were prepared by conventional solid-state sintering. The addition of Li+ and Bi3+ makes the orthorhombic-tetragonal phase transition temperature (TO-T) decrease from 200 °C for pure (K0.5 Na0.5) Nb O3 ceramics to -10 °C for KNLBN ceramics (x=0.06, y=0.005), while maintaining high Curie temperature (TC =455 °C) and piezoelectric properties (d33 =185 pCN, kp =0.43, kt =0.45, ε33T ε0 =1020, and tan δ=0.023) at room temperature. In addition, good temperature stability of electrical properties is obtained in KNLBN ceramics (x=0.06, y=0.005) owing to the decrease of TO-T. These results indicate that KNLBN (x=0.06, y=0.005) ceramic is a promising lead-free piezoelectric candidate material for high temperature applications.